• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.6
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• pp.55-62
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• 2014

Torrefaction is considered as a promising pre-treatment for thermochemical utilization of biomass. Torrefaction temperature and time are the critical operation parameters. In this study, investigated were the effects of reaction temperature and time on product composition of torrefaction. scanning electron microscope (SEM) images and thermo gravimetric analyzer (TGA) results were also compared for the effects of the operating parameters. SEM images showed that the pores were observed at the temperature of $250^{\circ}C$ for 30 minutes. Rapid decreases in weight were observed the temperature between 200 and$400^{\circ}C$. Higher heating value of the torrefied biomass was over 5,000 kcal/kg at the temperature of $250^{\circ}C$ for 45 minutes. Energy density, which is defined as the ratio of the energy yield over the mass yield was 1.36 at the temperature of $250^{\circ}C$ for 45 minutes. The energy density was higher up to 1.6 at the temperature of $280^{\circ}C$, which indicates greater loss in mass. The major components of the gas produced in the torrefaction were $CO_2$ and CO, with traces of methane. The total amount of gas was 31.54 l/kg and the calorific value of the gas was $1,164.4Kcal/Nm^3$ at the temperature of $250^{\circ}C$ for 30 minute reaction time. Based on the results of this study, the temperature of effective torrefaction is about $250^{\circ}C$ for 30 to 45 minutes of reaction time. Considering the heating value, it is desirable to utilize the gas for efficient process of torrefaction.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.5
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• pp.120-127
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• 2009

An electric furnace, inside which desired temperatures are kept constant by generating heat, is known to be a difficult system to control and model exactly because system parameters and response delay time vary as the temperature and position are changed. In this study the heating system of ceramic drying furnaces with time-varying parameters is mathematically modeled as a second order system and control parameters are estimated by using a RIV (Recursive Instrumental-Variable) method. A modified bang-bang control with magnitude tuning is proposed in the time optimal temperature control of ceramic drying electric furnaces and its performance is experimentally verified. It is proven that temperature tracking of adaptive time optimal control using a second order model is more stable than the GPCEW (Generalized Predictive Control with Exponential Weight) and rapidly settles down by pre-estimation of the system parameters.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.148.2-148.2
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• 2013

We prepared hydrophobic PDMS-coated porous silica as pre-concentration adsorbent for chemical warfare agents (CWAs). Since CWAs can be harmful to human even with a small amount, detecting low-concentration CWAs has been attracting attention in defense development. Porous silica is one of the promising candidates for CWAs pre-concentration adsorbent since it is thermally stable and its surface area is sufficiently high. A drawback of silica is that adsorption of CWAs can be significantly reduced due to competitive adsorption with water molecule in air since silica is quite hydrophilic. In order to solve this problem, hydrophobic polydimethylsiloxane (PDMS) thin film was deposited on silica. Adsorption and desorption of chemical warfare agent (CWA) simulants (Dimethylmethylphosphonate, DMMP and Dipropylene Glycol Methyl Ether, DPGEM) on bare and PDMS-coated silica were studied using temperature programed desorption (TPD) with and without co-exposing of water vapor. Without exposure of water vapor, desorbed amount of DMMP from PDMS-coated silica was twice larger than that from bare silica. When the samples were exposed to DMMP and water vapor at the same time, no DMMP was desorbed from bare silica due to competitive adsorption with water. On the other hand, desorbed DMMP was detected from PDMS-coated silica with reduced amount compared to that from the sample without water vapor exposure. Adsorption and desorption of DPGME with and without water vapor exposing was also investigated. In case of bare silica, all the adsorbed DPGME was decomposed during the heating process whereas molecular DPGME was observed on PDMS-coated silica. In summary, we showed that hydrophobic PDMS-coating can enhance the adsorption selectivity toward DMMP under humid condition and PDMS-coating also can have positive effect on molecular desorption of DPGME. Therefore we propose PDMS-coated silica could be an adequate adsorbent for CWAs pre-concentration under practical condition.

• Journal of Astronomy and Space Sciences
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• v.34 no.4
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• pp.251-256
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• 2017

The electric coupling between the lithosphere and the ionosphere is examined. The electric field is considered as a timevarying irregular vertical Coulomb field presumably produced on the Earth's surface before an earthquake within its epicentral zone by some micro-processes in the lithosphere. It is shown that the Fourier component of this electric field with a frequency of 500 Hz and a horizontal scale-size of 100 km produces in the nighttime ionosphere of high and middle latitudes a transverse electric field with a magnitude of ~20 mV/m if the peak value of the amplitude of this Fourier component is just 30 V/m. The time-varying vertical Coulomb field with a frequency of 500 Hz penetrates from the ground into the ionosphere by a factor of ${\sim}7{\times}10^5$ more efficient than a time independent vertical electrostatic field of the same scale size. The transverse electric field with amplitude of 20 mV/m will cause perturbations in the nighttime F region electron density through heating the F region plasma resulting in a reduction of the downward plasma flux from the protonosphere and an excitation of acoustic gravity waves.

• Journal of Hydrogen and New Energy
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• v.20 no.5
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• pp.439-446
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• 2009

This paper investigates the dehydration and RDF (Refuse Derived Fuel) production of organic wastes, livestock manure and sewerage sludge with pressurized hydrothermal treatment process. The renewable technology for the organic wastes must involve short treatment time required, reusable energy source, anti-odor and viruses, low cost for the treatment, and well-fertilization. The pressurized hydrothermal treatment process promotes to evaporate moisture in the waste after being shortly treated in a reactor, which uses steam and heat supplied by an external boiler. By the pressurized steam, the cell walls of the waste break and effectively release the internal moisture. Then, the dried waste can be mixed with waste vinyls to produce RDF with a higher heating value as high as 6,700 kcal/kg.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.948-951
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• 2008

Ubiquitous sensor network (USN) based on ZigBee communication protocol has been used in various application fields, such as home-network, intelligent building and machine, logistics, environmental monitoring, military field, security field and etc. The ZigBee is targeted at radio-frequency application that require a low data rate, long battery life and secure network. Especially, the USN system can be applied efficiently to building-indoor where the complex geometry is adopted. In this study, all 90 points of railway cabin indoor were monitored for temperature and humidity using USN technology. All sensors were pre/post-calibrated and the temperature/humidity change were analyzed in a railway cabin in real-time. The results would be useful to develop the cabin heating, ventilating and air conditing (HVAC) system to meet all passengers' thermal comfort regardless of their seat position.

• Mycobiology
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• v.43 no.3
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• pp.272-279
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• 2015

To screen molecular chaperones similar to small heat shock proteins (sHsps), but without ${\alpha}$-crystalline domain, heat-stable proteins from Schizosaccharomyces pombe were analyzed by 2-dimensional electrophoresis and matrix assisted laser desorption/ionization time-of-flight mass spectrometry. Sixteen proteins were identified, and four recombinant proteins, including cofilin, NTF2, pyridoxin biosynthesis protein (Snz1) and Wos2 that has an ${\alpha}$-crystalline domain, were purified. Among these proteins, only Snz1 showed the anti-aggregation activity against thermal denaturation of citrate synthase. However, pre-heating of NTF2 and Wos2 at $70^{\circ}C$ for 30 min, efficiently prevented thermal aggregation of citrate synthase. These results indicate that Snz1 and NTF2 possess molecular chaperone activity similar to sHsps, even though there is no ${\alpha}$-crystalline domain in their sequences.

• Nuclear Engineering and Technology
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• v.54 no.3
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• pp.1145-1151
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• 2022

A hybrid cutting using both plasma and end mill was developed for safe and efficient dismantling of nuclear facilities. In this cutting method, a moving arc plasma heats up the workpiece before milling. Thermally softened part of the workpiece is then removed quickly and deeply with an end mill. For the cutting experiments, a three-axis numerical control (NC) milling machine was combined with a commercialized arc plasma torch and used to cut 25 mm thick stainless steel plates. Experimental results revealed that pre-heating by arc plasmas can improve the cutting volume per unit time higher than 40% by reducing the cutting load and increasing the cuttable depth when using an end mill without cutting fluids. These advantages of a hybrid cutting process are expected to contribute to quick and safe segmentations of metal structures with radioactively contaminated inner surfaces.

• Korean Journal of Agricultural and Forest Meteorology
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• v.7 no.3
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• pp.185-191
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• 2005

An accurate prediction of dormancy release and bud burst in temperate zone fruit trees is indispensable for farmers to plan heating time under partially controlled environments as well as to reduce the risk of frost damage in open fields. A thermal time-based two-step phenological model that originated in Italy was applied to two important grapevine cultivars in Korea for predicting bud-burst dates. The model consists of two sequential periods: a rest period described by chilling requirement and a forcing period described by heating requirement. It requires daily maximum and minimum temperature as an input and calculates daily chill units (chill days in negative sign) until a pre-determined chilling requirement for rest release is met. After the projected rest release date, it adds daily heat units (anti-chill days in positive sign) to the chilling requirement. The date when the sum reaches zero isregarded as the bud-burst in the model. Controlled environment experiments using field sampled twigs of 'Campbell Early' and 'Kyoho' cultivars were carried out in the vineyard at the National Horticultural Research Institute (NHRI) in Suwon during 2004-2005 to derive the model parameters: threshold temperature for chilling and chilling requirement for breaking dormancy. The model adjusted with the selected parameters was applied to the 1994-2004 daily temperature data obtained from the automated weather station in the NHRI vineyard to estimate bud burst dates of two cultivars and the results were compared with the observed data. The model showed a consistently good performance in predicting the bud burst of 'Campbell Early' and 'Kyoho' cultivars with 2.6 and 2.5 days of root mean squared error, respectively.

• Journal of the Korean Ceramic Society
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• v.49 no.6
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• pp.620-624
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• 2012

The role of moisture remaining inside the deposition chamber during the formation of the cubic boron nitride (c-BN) phase in BN film was investigated. BN films were deposited by an unbalanced magnetron sputtering (UBM) method. Single-crystal (001) Si wafers were used as substrates. A hexagonal boron nitride (h-BN) target was used as a sputter target which was connected to a 13.56 MHz radiofrequency electric power source at 400 W. The substrate was biased at -60 V using a 200 kHz high-frequency power supply. The deposition pressure was 0.27 Pa with a flow of Ar 18 sccm - $N_2$ 2 sccm mixed gas. The inside of the deposition chamber was maintained at a moisture level of 65% during the initial stage. The effects of the evacuation time, duration time of heating the substrate holder at $250^{\circ}C$ as well as the plasma treatment on the inside chamber wall on the formation of c-BN were studied. The effects of heating as well as the plasma treatment very effectively eliminated the moisture adsorbed on the chamber wall. A pre-deposition condition for the stable and repeatable deposition of c-BN is suggested.